**6.6 Tracking of gas quality parameters in the network**

Online-simulation is used for tracking of gas quality parameter in the network. This method saves measuring equipment (gas chromatographs) in the field giving a much more detailed view of the way, value and distribution the gas quality parameters (see figure 6). Most often it will be applied for tracking the calorific value for all nodes on an hourly base (if used with historic data it will be called a reconstruction run). If the computed results shall be applied for billing purposes, then an official acknowledgement/permit of the technical authority (board of weights and measures) is required and a permanent surveyance system has to be installed.

all pipes but moderate number of measurement points making modeling an intensive work. The network structure of a distribution system tends to be strongly intermeshed. Distribution networks may have also a smaller trunk transportation system at a higher pressure level (e.g. 25, 16, 10 or 4 bar) while most of the pipes in the final distribution area

Intermeshing is a basic concept in pipeline/network planning: it provides intrinsic redundancy for gas delivery in case of trouble/break at single points of pipeline. It supports continuous operation and pressure of the system; as it is most important to keep the whole pipeline system under pressure all the time (if the pressure would drop to zero, oxygen could enter the pipeline system exposing some areas or the system to the risk of explosion). Exaggerated use of intermeshing lead to higher investment cost in pipes and decrease a costefficient network structure in principle (besides, an item of passionate discussions among planners). Intermeshed networks need, because of their complexity, simulation support to

An advanced feature of simulation or operating mode is online-simulation. Here the simulation is coupled with a SCADA system and is executed corresponding to the cycle of the data acquisition (minutes to hours). It is a good tool to watch and control the network by additional detailed information almost in real time. This type of simulation is very demanding as it requires correct and complete data all the time what must be carefully prepared. Offline-simulation is the normal application it can be executed when needed - at

Static simulation means to execute a simulation for a fixed time; it is therefore good and often used for checking a set of scenarios or planning alternatives. Dynamic simulation reflects the changes of variables over time. This can be applied for historical data or for the future (based on forecasts). In case of reconstruction and tracking of certain values in the network (e.g. gas quality, calorific value) dynamic simulation is required. The typical time scale for simulations are hours which correspond well to most of the measurement cycles

Online-simulation is used for tracking of gas quality parameter in the network. This method saves measuring equipment (gas chromatographs) in the field giving a much more detailed view of the way, value and distribution the gas quality parameters (see figure 6). Most often it will be applied for tracking the calorific value for all nodes on an hourly base (if used with historic data it will be called a reconstruction run). If the computed results shall be applied for billing purposes, then an official acknowledgement/permit of the technical authority (board of weights and measures) is required and a permanent surveyance system has to be installed.

are operated at 0.022 to 0.8 bar depending on the required flows.

get detailed insight into physical state and variables of the pipeline system.

**6.3 Influence of intermeshing** 

**6.4 Online- and offline-simulation** 

**6.5 Static vs. dynamic simulation** 

which are read from the field devices.

**6.6 Tracking of gas quality parameters in the network** 

arbitrary time.

Fig. 6. Schematic view of areas of influence from different input of calorific values at feeding points
